Cross-built FreeBSD aarch64 archives were not possible: package.sh took the
arch from uname -m (the x86_64 VM host), built for the host, read binaries
from target/release, and ran the aarch64 gridcraft-cli to print its version.
When CARGO_BUILD_TARGET is set, build with --target, read from
target/<triple>/release, name the archive by the target's arch (aarch64 for
aarch64-unknown-freebsd, x86_64 otherwise), and skip running the binary.
Unset behavior is unchanged.